125I-labelled human chorionic gonadotrophin (hCG) as an elimination marker in the evaluation of hCG decline during chemotherapy in patients with testicular cancer

Kinetic-exclusion analysis-based immunosensors versus enzyme-linked immunosorbent assays for measurement of cancer markers in biological specimens

Kinetic exclusion analysis (KinExA)-based immunosensors and enzyme-linked immunosorbent assays (ELISA) have been developed and validated for measurement of five different cancer markers in biological specimens. These markers were: 2'-deoxycytidine (dCyd), 8-hydroxy-2'-deoxyguanosine (8HdG), carbohydrate antigen (CA15-3), α-fetoprotein (AFP), and β-subunit of human chorionic gonadotropin (β-HCG). The KinExA-based assays were conducted on the KinExA™ 3200 instrument. The ELISA assays employed the competitive immunoassay format for dCyd and 8HdG, however they employed the direct sandwich-type format for CA15-3, AFP, and β-HCG. Each assay was validated in terms of its limit of detection, working range, precision profile, and accuracy. The analytical performances of the KinExA-based sensors were found to be superior to the ELISA for the five markers. The data demonstrated that the format of the assay may influence its performance characteristics (sensitivity, precision, etc.), even when exactly the same reagents are employed. The superior performance of the KinExA format is most likely due to: (1) the high surface area of beads containing the immobilized capture in the flow cell of the instrument, (2) the high flow rate of the reagents passing through the beads, which minimizes the diffusion limitations at the reaction surface, and (3) the limited time that the antibody is in contact with the capture reagent. The KinExA-based assays exhibited three noteworthy properties compared with ELISA: (1) avoiding the problems of mass transport limitations, and mobility effects, (2) KinExA analysis with automated sampling increase the assay convenience; and (3) providing high sensitivity with a lower limit of detection and better precision than ELISA. The proposed KinExA-based immunosensors are anticipated to have a great value in measurement of the cancer markers where more confident results are needed.

Early prediction of treatment response to high-dose salvage chemotherapy in patients with relapsed germ cell cancer using [(18)F]FDG PET

To assess the ability of [(18)F]fluorodeoxyglucose positron emission tomography for the early prediction of response in patients with relapsed metastatic germ cell tumours undergoing salvage high-dose chemotherapy. The role of positron emission tomography was compared with established means of tumour response assessment such as CT scans/MRI and serum tumour marker changes. In addition, positron emission tomography was compared with a current prognostic score which differentiates three prognostic groups with failure-free survival rates ranging from 5-50%. [(18)F]fluorodeoxyglucose uptake of metastases from germ cell tumours as well as CT scans and serum tumour marker were acquired after 2-3 cycles of induction chemotherapy but before the start of high-dose chemotherapy and CT scans/serum tumour marker were compared with the baseline examinations in 23 patients with relapsed germ cell tumours. To evaluate the validity of early response prediction by positron emission tomography, radiological monitoring and serum tumour marker decline, histopathologic response after resection of residual masses and/or the clinical course over 6 months after the end of treatment (relapse vs freedom of progression) were used. Overall, 10 patients (43%) achieved a marker-negative partial remission, three (13%) a marker-positive partial remission, five (22%) a disease stabilization and five (22%) progressed during treatment. Nine patients (39%) remained progression-free over 6 months following treatment, whereas 14 (61%) progressed. The outcome of high-dose chemotherapy was correctly predicted by positron emission tomography/CT scan/serum tumour marker in 91/59/48%. Eight patients with a favourably predicted outcome by CT scans plus serum tumour marker but a positive positron emission tomography prior to high-dose chemotherapy, failed treatment. This results in the following sensitivities/specificities for the prediction of failure of high-dose chemotherapy: positron emission tomography 100/78%; radiological monitoring 43/78%; serum tumour marker 15/100%. The positive and negative predictive values of positron emission tomography were 88 and 100%, respectively. As compared with the prognostic score, positron emission tomography was correctly positive in all patients of the three risk groups who failed treatment. In addition, a negative positron emission tomography correctly predicted a favourable outcome in the good and intermediate group. [(18)F]fluorodeoxyglucose positron emission tomography imaging can be used to assess response to chemotherapy in patients with relapsed germ cell tumours early in the course of treatment and may help to identify patients most likely to achieve a favourable response to subsequent high-dose chemotherapy. In patients with response to induction chemotherapy according to CT scans or serum tumour marker evaluation, positron emission tomography seems to add information to detect patients with an overall unfavourable outcome. It may also be a valuable addition to the prognostic model particularly in the good and intermediate group for further selection of patients who will profit from high-dose chemotherapy.

Prognostic parameters for the management of advanced testis tumours

The need for prognostic parameters in testicular germ cell tumours is sometimes questioned based on an overall cure rate of more than 80% of the patients regardless of tumour stage. However, the trend for an earlier and more accurate diagnosis amenable to curative treatment as well as the high effectiveness of standard Cisplatinum containing chemotherapy has masked the continuing need for intensifying therapy in patients with adverse risk factors. This intense treatment is often associated with worrysome morbidity and the assessment of prognostic factors, stage by stage, is warranted on which patient at risk can be identified and treated accordingly. Traditional prognostic factors, on which most classification systems are based, include large tumour volume, the presence of liver, bone or brain metastasis, grossly elevated tumour markers and an extragonadal primary site, particularly in the mediastinum. Novel prognostic factors are either (1) independent from the patient and his disease, (2) inherent on the patient's characteristics or (3) based on tumour biology. Clearly, the infrastructure and the experience of the treating uro-oncology unit (see 1) is decisive for treatment outcomes, and -at least-'difficult to treat' patients should be referred to properly resourced cancer centres. Patients with higher socio-economic status, willing to travel and well educated enough to be worried about their diseases status apparently gain access to expert centres more easily (see 2), translating into an upgrade on prognosis. Finally, biologic factors (see 3) such as beta-human chorionic gonadotrophin or MAGE epitopes in seminoma or the percentage of embryonal carcinoma components orvascular invasion mayor may not inversely influence the prognosis and need further assessment in prospective trials. However, the search for even better (molecular) biologic factors is speeding up because more complex treatment decisions such as in advanced testicular cancers rely on a more precise determination of prognosis, enabling a more tailored selection of individualized therapeutic options.

Current opinion in germ cell cancer 2000

Despite its relative rarity compared with the common adult cancers, scientific and clinical interest in germ cell cancer is increasing. From the point of view of epidemiology, the controversy about the relative importance of intrauterine versus postpubertal risk factors has continued. Evidence to support the importance of intrauterine factors comes from reports from Norway, Canada, and the US, confirming the Danish observation that the rising incidence of germ cell cancer is linked to a birth cohort effect; evidence in support of the importance of postpubertal risk comes from three case/control studies demonstrating increased risk linked to postpubertal exposures such as pesticides, plastics, electromagnetic radiation, trauma, and infections. There has been increasing interest in human endogenous retrovirus K10 as a possible factor explaining genetic susceptibility and providing a linkage between the two groups of risk factors. In cytogenetics, progress was reported in identifying the deletion point of the suspected tumor suppressor gene responsible for the i12p marker chromosome abnormality and development of FISH probes for diagnostic purposes. In molecular biology, the importance of DNA repair deficiency in normal germ cells as a factor in the exquisite chemosensitivity of germ cell cancer has been high-lighted by a report demonstrating a low level of the xeroderma pigmentosa group A (XPA) protein and induction of resistance in vitro by adding XPA. In the clinic, progress in positron emission tomography scanning and laparoscopic lymph node staging are leading to changes in outlook on management of stage 1 cases and patients with small residual masses postchemotherapy. Salvage chemotherapy regimens integrating dose dense and vertical dose intensification strategies reported 60% progression-free survival. New drugs such as gemcitabine demonstrated continued therapeutic potential for chemotherapy in these tumors. A report demonstrating the inadequacies of hormone replacement after bilateral orchidectomy and a report of the first child born after testis-conserving therapy highlight the need for more attention to testis conservation as a quality of life issue. With the cure rates so high, the need for central referral is once again debated both for stage 1 and metastatic disease. With new ways of defining poor risk stage 1 patients and reports on impact of experience highlighting the worse outcome of patients treated in centers treating small numbers, views on this issue remain clearcut.

Validation of 125I-hCG as a marker for elimination of hCG and stability of 125I-hCG after in vivo injection in humans

We have recently introduced 125I-hCG as an elimination marker in patients with human chorionic gonadotrophin (hCG) producing testicular cancer. 125I-hCG is a well-known reagent in clinical biochemistry and is used extensively in hCG assays. Previous studies have shown that the iodination process leaves the hCG molecule mainly intact. The iodination, purification and stability of 125I-hCG tracer are described. The aim of the present study was to determine whether or not 125I is associated with hCG after the injection of 125I-hCG intravenously (i.v.) in humans. Three different methods were used. Following injection of 125I-hCG, the plasma disappearance of radioactivity and hCG were followed for a period of 28 days in 13 normal subjects. Serum from a normal healthy male following injection of 125I-hCG was analysed using a double antibody direct binding radioimmunoassay specific for holo-hCG and high performance liquid chromatography (HPLC). Following injection of 125I-hCG in eight normal healthy males and five normal healthy females, the disappearance of radioactivity and hCG showed identical paths in the 28 days follow-up period. The bindable radioactive fraction of immunologically active hCG in serum of a normal healthy male following injection of 125I-hCG was between 57.0% and 72.1%, and was constant over time. HPLC showed similar elution pattern of serum from a normal healthy male injected i.v. with 125I-hCG and 125I-hCG. Using three different methods, we were able concurrently to demonstrate the association of 125I with hCG in humans up to 28 days after injection of radiolabelled hCG i.v. Thus, information about the expected elimination of hCG can be obtained by following the elimination of activity in plasma after injection of 125I-hCG.